Trigonometry: A Clever Study Guide is a book by James Tanton
James Tanton (a very interesting mathematician interested in HS student understanding):
YouTube: example (tetrahedron problem) 😉
James Tanton (PhD. Mathematics, Princeton University, 1994) is a research mathematician deeply interested in bridging the gap between the mathematics experienced by school students and the creative mathematics practiced and explored by mathematicians. He worked as a college professor for a decade, as a high-school teacher for a decade, and is now the Mathematician in Residence at the Mathematical Association of America in Washington D.C.